1. Field of the Invention
The present invention relates to an electrically activated fluid pump having a valveless non-working chamber resonantly responsive to sequenced exobaric pulsation.
2. Description of the Related Art
Industrial and aerospace fluid pumps are subjects of continuous development to increase operating temperature range, achieve longer life through greater reliability, and to reduce manufacturing cost by simplifying design to in part offset the use of costlier materials.
In reference U.S. Pat. No. 3,743,446 issued Jul. 3, 1973, Mandroian describes his resonant pump consisting of a non-working chamber (in the sense that there is no gross movement of a chamber wall portion such as a piston) having a flexible diaphragm chamber wall portion that is oscillated by an electrical transducer, and fluid inlet and outlet ports. The diaphragm oscillation stimulates a standing wave having pressure nodes and velocity nodes (pressure antinodes). The fluid inlets and fluid outlets of the chamber are arranged proximate the respective nodes. Mandroian is correct that at instants of positive pressure a pressure node near an outlet forces fluid thereout. Mandroian is also correct that at instants of negative pressure at a pressure antinode near an inlet induces fluid therein. Mandroian concludes that fluid exiting the outlets and fluid entering the inlets constitute a pumping action, which is indeed correct. However, Mandroian overlooked the fact that the pressure at a pressure node passes through alternating positive and negative maxima, that the pressure node is stationary in a standing wave, and therefore, at a half period of time later than the time fragment illustrated by Mandroian's FIG. 2, the conditions will be reversed, namely, flow direction arrows will be reversed from those shown. Therefore, fluid portions proximate inlets and outlets simply oscillate instead of being pumped. Mandroian overlooked the fact that, in a standing wave, the time averages of fluid particle pressure, velocity, and fluid particle displacement, are all essentially zero. Therefore the pump would not work unless it had valves at the inlet and output ports, which it did not have.
A disadvantage of Mandroian's pump, and pumps in general, is reliance on mechanical transducing means. In Mandroian the two mechanical transducing means described for stimulating resonance in the fluid of the pumping cavity are a core with a current coil interacting with a magnetic slug, and a piezoelectric crystal. Both magnetic and electrostrictive transducers have an operating temperature range bounded by Curie temperature(s) outside of which satisfactory operation, and possibly even survivability, is not possible. Another disadvantage of Mandroian's pump, had it worked as described, is the range of frequencies over which operation is possible. His apparatus is described as an electromechanical oscillator in which chamber length, fluid state, elastic nature of the diaphragm, and the electrical elasticity of the driving electrical circuit all contribute to initiating and sustaining chamber resonance. The diaphragm is described as being designed to vibrate at a predetermined frequency, implying at most a relatively limited range of operating frequencies.
Applicant's copending patent applications Ser. No. 07/870,885 filed Apr. 20, 1992 and Ser. No. 07/807,667 filed Dec. 16, 1991 a continuation-in-part of Ser. No. 07/697,368 filed May 9, 1991 are hereby made a part hereof and incorporated herein by reference. The applications describe methods and apparatus using a multiplicity of small and highly responsive electric resistance heaters. A current pulse exobarically stimulates proximate fluid which in turn produces useful mechanical work. Each heater, and alternatively, each heater group, is independently electrically activated to create predetermined spatial and temporal distributions of fluid dynamic force. The heaters do not rely on Curie temperatures for proper operation and survivability, and therefore operate in a range of temperatures significantly wider than that of all (excluding capacitors) other known electrical components. Methods are described in which a fluid body adjunct to the multiplicity of heaters is perturbed, such perturbations clearly including the stimulation of acoustic waves.